How long does a mouse pregnancy last? - briefly
Gestation in mice generally spans 19–21 days. Slight variations of one to two days may appear among different strains or environmental conditions.
How long does a mouse pregnancy last? - in detail
The gestation period for the common laboratory mouse typically spans 19 – 21 days from conception to delivery. This interval is shorter than that of most mammals and is influenced by genetic strain, ambient temperature, and maternal nutrition.
During the gestational timeline, embryonic development proceeds through distinct stages:
- Days 0 – 3: fertilization and implantation of the blastocyst in the uterine wall.
- Days 4 – 7: formation of the embryonic disc and initiation of organogenesis.
- Days 8 – 12: rapid growth of the embryo, development of limb buds, and differentiation of major organ systems.
- Days 13 – 15: maturation of the central nervous system, appearance of hair follicles, and preparation of the respiratory system.
- Days 16 – 18: final organ refinement, accumulation of fetal fluids, and positioning for birth.
- Days 19 – 21: parturition, typically occurring during the dark phase of the light‑dark cycle.
Litter size averages four to eight pups, though larger litters can extend the gestation by a day or two due to increased uterine load. Environmental stressors, such as temperatures below 20 °C, may prolong the period by up to 24 hours, while optimal conditions (22 – 24 °C, balanced diet) maintain the standard duration.
Post‑delivery, pups remain in the nest for approximately 21 days before weaning, during which they undergo rapid growth and sensory maturation. Understanding the precise timing of each developmental phase assists researchers in scheduling experimental interventions and interpreting physiological outcomes.